Parenthetical Expressions

These are expressions, bounded by commas, which give clarity to a sentence. 
A example is :
" Yoghurt, on the other hand, is a fine substitute for ice-cream".

Some other common parenthetical expressions are :
after all
by the way
for example
however
in my opinion
naturally
incidentally
of course
on the contrary
on balance
to tell you the truth
indeed
in fact
honestly speaking
bluntly speaking
in short
Yes, we have all heard them and used them; this is their proper name!